Selecting two random (different)column values - seems tricky

[sbasak1]

A table has two columns - firstname & lastname

Now, I want to randomly select a firstname and lastname.
The trick is, the firstname and lastname must NOT be selected from same row!

I tried to use dbms_random.value(1,1000) and got the names, the problem is how do I concat the two fields

If I use

select firstname, lastname from customer where....

then I get values from same row!

Thanks